Saner package exports

[mephenor]

Restructured imports to conform to the following rules:

1. Only the needed minimum is available in each (sub)package __init__.py
2. Lateral imports directly from a module are allowed (and prefered) within a package, everything else that should be accessed should be exposed in and imported from the corresponding __init__.py
3. Minimize the amount of imports from higher level packages
4. The central main.py is allowed to import directly from lower level packages

This also introduces a mixed import style, i.e. imports within the same package are now relative for better readability, so it's clear what's local and which module might have some complexity distributed across the code base.

Also moved config and work_package up one level and removed clamping for the exponential_backoff value.

[coveralls]

Pull Request Test Coverage Report for Build 10903432722

Details

• 67 of 76 (88.16%) changed or added relevant lines in 22 files are covered.
• 74 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-1.6%) to 71.173%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ghga_connector/core/uploading/api_calls.py	0	4	0.0%
src/ghga_connector/cli.py	15	20	75.0%

Files with Coverage Reduction	New Missed Lines	%
src/ghga_connector/core/uploading/api_calls.py	74	0.0%

Totals
Change from base Build 10830020336:	-1.6%
Covered Lines:	995
Relevant Lines:	1398

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💛 - Coveralls